In digital photography, images are typically formed by passing light from an object through an objective and infrared (IR) filter onto an image sensor or image capture unit such as a CMOS or CCD unit. The image capture unit typically comprises some millions of pixel sensing elements for forming corresponding pixels of digital images. Modern digital cameras typically have automatic focus control (AF), automatic exposure (AE) i.e. adjustment of the opening of the dimming shutter and automatic white balance adjustment (AWB) for producing images that look good.
During the development of digital cameras, numerous improvements have been made in each of the aforementioned AF, AE and AWB. Typically they still operate so that one or more objects of interest are identified in images produced by the image sensor and then the image capture unit is adjusted to optimize the appearance of the objects of interest. For example, a face can be detected based on characteristic features of faces, the focus be adjusted such that the face is in focus e.g. so that contrast between adjacent points is at its maximum. The exposure can be so controlled that with a reasonable shutter period and the amplifier gain controlling the sensitivity of the sensor output (corresponding to ISO setting), the pixels of images become sufficiently illuminated to make dark parts of images perceivable while the pixels of bright parts of images do not become too much illuminated. The white balance is adjusted so that the colors of the images would appear natural. For instance, the proportional light intensities measured in different three color channels of the image sensor can be compared to pre-set parameters that characterize typical illuminants. Then, the brightness of pixels of each color channel is adjusted to compensate for the typical deviation from that caused by natural light.
The adjustment of the AF, AE and AWB is typically performed in a cycle in which all these three different important factors of digital photography become gradually adjusted. In video imaging, rapid changes are often avoided in order to avoid nauseous appearance of produced video footage.